1. Field of the Invention
This invention relates to an exposure controlling system for an interchangeable lens and an interchangeable lens which are particularly suitable for exposure control of a single lens reflex camera for which a cata-dioptric lens is provided as one of interchangeable lenses.
2. Description of the Prior Art
Conventionally, single lens reflex cameras having AE (automatic exposure) and AF (automatic focusing) functions of the TTL (through the lens) type have been put to practical use. As interchangeable lenses for such single lens reflex cameras, various lenses have been developed wherein information regarding AE and AF functions is fixedly stored such that it may be read from a body of a camera on which the lens is mounted.
It has been proposed for such a single lens reflex camera to make exposure control of the stopping down light measuring method when mounting of an interchangeable lens is not confirmed. However, such exposure control is not prepared for mounting of a catadioptric lens.
Such a single lens reflex camera having AE and AF functions of the TTL type as described above is not prepared for use of a cata-dioptric lens as an interchangeable lens principally from a restriction in detection of a focus condition. Accordingly, no consideration is given either to exposure control for coping with a cata-dioptric lens. While cata-dioptric lenses which can be mounted on such a single lens reflex camera are on the market, if a cata-dioptric lens is mounted on such a single lens reflex camera as described above, the body of the camera cannot read necessary information from the interchangeable lens. Consequently, the camera body will not conduct detection of a focus condition and will make the same exposure controlling operation as that when no interchangeable lens is mounted. Accordingly, there is a problem that functions of the camera body are restricted significantly when a cata-dipotric lens is used.